Filament machine sewing thread

ABSTRACT

A filament machine sewing thread comprising a spun combined filament yarn obtained by combining polyester filaments A having an intrinsic viscosity [η] F  within the range of 0.7 to 1.2 with polyester filaments B having a lower intrinsic viscosity [η] F  than that of the polyester filaments A by 0.2 to 0.7 and a higher elongation than that of the polyester filaments A in a spinning stage.

This application is a 371 of PCT/JP02/08277 filed Aug. 14, 2002.

TECHNICAL FIELD

The present invention relates to a filament machine sewing threadcapable of forming uniform stitches while leaving gloss of filaments andhaving good high-speed sewability.

BACKGROUND ART

Filament machine sewing threads have been used for various kinds ofsewing because of gloss as compared with that of machine sewing threadscomprising spun yarns, uniform stitches and a high machine sewing threadstrength; however, the filament machine sewing threads havedisadvantages in that sewability in back stitching and zigzag chainstitching readily causing untwisting is inferior to that of the spunyarn machine sewing threads.

As for causes thereof, it is thought that drawing is carried out whileapplying a high thermal history using a polymer having a higherintrinsic viscosity than that of conventional polymers in order toretain the machine sewing thread strength which is a feature of thefilament machine sewing threads at a high value, and that the torque ofthe primary and final twists applied in the subsequent step of formingthe machine sewing threads is thereby not sufficiently set even afterdyeing of the machine sewing threads to cause untwisting and theformation of stitches is not successful when carrying out the backstitching and zigzag chain stitching.

In order to solve the problems, JP-A 5-106134 (hereunder, JP-A means“Japanese Unexamined Patent Publication”) discloses that a machinesewing thread having excellent sewability is obtained by forming acomposite from two kinds of filament yarns having a difference inelongation of 20% or above and forming loops or slacknesses with thehigh-elongation yarn. In the machine sewing thread, however, there areproblems that separation of the two kinds of filament yarns occurs and abias is caused in the form of stitches to deteriorate uniformity or adifference in dyeability is conspicuous when the machine sewing threadis dyed.

JP-A 9-78335 discloses a filament machine sewing thread obtained byspinning and combining a filament yarn having a high birefringence witha filament yarn having a low birefringence and arranging the filamentyarn having the low birefringence in a sheath part. The machine sewingthread has problems that the strength is lowered, the thread slips downfrom a bobbin, smooth thread feed cannot be made, breakage sometimesoccurs and handleability is bad as compared with that of conventionalfilament machine sewing threads because only the difference inbirefringence is utilized.

It is an object of the present invention to improve disadvantages causedby the formation of loops or slacknesses as described above and toprovide a filament machine sewing thread capable of forming uniformstitches while leaving the gloss of filaments and having good high-speedsew ability.

DISCLOSURE OF THE INVENTION

As a result of intensive studies made to achieve the objects, thepresent inventors have found out that a desired filament machine sewingthread is obtained by suitably controlling the intrinsic viscosity[η]_(F) and elongation of the filaments constituting the spun combinedfilament yarn within specific ranges. Thus, according to the invention,there is provided a filament machine sewing thread comprising a spuncombined filament yarn in which polyester filaments A₁ having anintrinsic viscosity [η]_(F) within the range of 0.7 to 1.2 and polyesterfilaments B having a lower intrinsic viscosity [η]_(F) than that of thepolyester filaments A by 0.2 to 0.7 and a higher elongation than that ofthe polyester filaments A are combined in a spinning stage.

BEST MODE FOR CARRYING OUT THE INVENTION

The mode for carrying out the invention will initially be detailedhereinafter.

In the present invention, the filament machine sewing thread is obtainedby the so-called spinning filament combining method for simultaneouslyspinning polyester filaments A and polyester filaments B, then doublingthe filaments A and B and simultaneously winding the doubled filaments.

Specifically, methods for leading polyester polymers different inintrinsic viscosity to the same spinneret, extruding the polyesterpolymers from separate discharge holes without mixing and winding thefilaments together using a usual conjugate spinning machine or the likeor methods for individually extruding the respective polymers fromindividually independent spinnerets, then doubling the filaments andwinding the doubled filaments or the like can be adopted. In short, anymethods may be used when both the filaments are united before completingthe winding after the spinning.

Examples of the polyester used in the present invention includepolyethylene terephthalate (hereinafter abbreviated to PET),polypropylene terephthalate, polybutylene terephthalate and the like.PET is most preferably exemplified.

It is necessary that the intrinsic viscosity of the polyester filamentsA is high from aspects of heat resistance, abrasion resistance andstrength, and it is necessary that the intrinsic viscosity [η]_(F) ofthe spun filaments is within the range of 0.7 to 1.2. When the intrinsicviscosity exceeds 1.2, a large-scaled apparatus is required forpolymerization and the cost is increased.

A polyester having a lower intrinsic viscosity [η]_(F) than theintrinsic viscosity [η]_(F) of the low-elongation filaments by 0.2 to0.7 is used as the polyester filaments B. This is because the intrinsicviscosity of polyester filaments B is reduced to keep the polyesterfilaments B in a state of scarcely producing a thermal stress and thepolyester filaments A having the residual torque is embraced with thepolyester filaments B to thereby prevent the torque of the machinesewing thread from developing when carrying out the back stitching andzigzag stitching. In order to prevent the torque from developing, adifference in intrinsic viscosity of 0.2 or above is required. When thedifference exceeds 0.7, the tenacity of the polyester filament filamentsA becomes too low and breakage of single filaments occurs when sewing iscarried out by a sewing machine to cause disturbance of stitches andlowering of uniformity. The difference in intrinsic viscosity ispreferably 0.3 to 0.6.

The elongation of the polyester filaments B may be higher than that ofthe polyester filaments A; however, the elongation is usually higher forpolyester filaments having a lower intrinsic viscosity when the samespinning conditions are adopted.

In the present invention, it is preferably that the polyester filamentscontain an orientation inhibitor.

The orientation inhibitor herein refers to a substance having actions ofinhibiting the orientation of the polyester filaments B and increasingthe elongation. Specifically, examples of the orientation inhibitorinclude polystyrene polymers, polymethacrylate polymers orpolymethylpentene polymers and the like; however, the orientationinhibitor is not limited to the polymers.

Optional methods can be adopted as a method for including theorientation inhibitor. For example, the orientation inhibitor may beincluded in a polymerization process of PET or the polymers may be meltmixed with PET, extruded, cooled, then cut and formed into chips.Further, both in a chip state are mixed and then directly melt spun.

The content of the orientation inhibitor is preferably 0.5 to 8.0% byweight based on the total weight of the filaments. When the content islower than 0.5% by weight, effects on increase in elongation are notsufficiently produced. On the other hand, when the content exceeds 8.0%by weight, the strength of the filaments is extremely lowered and singlefilament breakage sometimes occurs even at low-speed rotation of asewing machine. The content of the orientation inhibitor is preferably0.5 to 5.0% by weight.

As mentioned above, the spinning filament combining method is adopted inthe present invention. This is because it is necessary to adopt aspinning and winding method so as to mix the polyester filaments A withthe polyester filaments B of the order of single filaments before thespinning and winding.

As a spinning filament combining method for especially providing goodmixing, the polyester filaments A and the polyester filaments B may bespun from the same spinneret in which discharge holes of the spinneretare randomly dispersed, a spinneret comprising outer circular holes andinner circular holes or a bisected type spinneret.

The spinneret temperature is set at a temperature suitable for both thepolymers when the polymers are extruded from the same spinneret;however, the spinneret temperature may respectively separately be setwhen separate spinnerets are used.

As for the spinning speed, the yarn strength after drawing is lowered ascompared with that of the yarn spun at a low spinning speed though adifference in elongation after drawing is increased with increasingspinning speed. Therefore, a high spinning speed may be selected if animprovement in productivity rather than the yarn strength is desired. Inaddition, the production may be performed by a method in which spinningis directly connected to drawing. A method for achieving drawing only byhigh-speed spinning may be adopted.

In the present invention, the polyester filaments A and the polyesterfilaments B may be combined with filament-intermingled treatment by theintermingle device with the air blast before or after taking up the spunfilaments. In the present invention, it is preferable that the filamentstrength of the polyester filaments A is higher and a filament strengthof at least 5.0 g/dtex or above is required. The preferable strength isat least 5.4 g/dtex or above. On the other hand, a filament strength of1.3 g/dtex or above withstanding friction or tensile stress when sewingis carried out by a sewing machine is required even in the case of thehigh-elongation filaments. The preferable strength is at least 1.5g/dtex or above. A strength of at least 4.0 g/dtex or above issufficient as the whole machine sewing thread. The preferable strengthis at least 4.3 g/dtex or above.

The mixing ratio of the polyester filaments A to the polyester filamentsB is preferably about 7:3 to 9:1. When the mixing ratio of thelow-elongation filaments is lower than 7:3, a stress required for themachine sewing thread is insufficient. On the other hand, when themixing ratio of the polyester filaments A exceeds 9:1, heat-settingproperties of the polyester filaments B are sometimes insufficient sothat it is difficult to suppress the development of torque of themachine sewing thread. The preferable range is 8:2.

Furthermore, the number of filaments in the polyester filaments A ispreferably 8 or more and the number of filaments in the polyesterfilaments B is preferably 3 or more in order to sufficiently mix thepolyester filaments A with the polyester filaments B. In the case of thenumber of combined yarns or less, a bias of mixing is sometimes causedto form nonuniform stitches. The sum total of the number of filaments inthe polyester filaments A and the polyester filaments B is preferablywithin the range of 15 to 48. When the number is larger than the range,it is undesirable that there are disadvantages in making the singlefilament fineness too fine and lowering the yarn strength. Further, itis undesirable that the filaments tend toward dulling from aspects ofgloss.

The machine sewing thread of the present invention provides a raw yarnfor the machine sewing thread having good sewability by utilizing adifference in heat-setting properties due to a difference in intrinsicviscosity and a difference in elongation without relying on loops orslacknesses as opposed to conventional machine sewing threads. In short,it is presumed that heat transfer is prevented to improve the sewabilitybecause sufficient heat-setting effects are produced and single filamentparts in the machine sewing thread in contact with a needle and a fabricduring sewing are randomly replaced by making the low-elongationfilaments and the high-elongation filaments in the machine sewing threadmoderately migrate even without forming large loops or slacknesses suchas the machine sewing thread disclosed in JP-A 5-106134.

Thus, in short, a part of the filaments have not suffered the frictionwith the needle or fabric for a long period and the single filamentparts are continually replaced and can be passed through the needle orfabric without the damage. Therefore, a machine sewing thread capable ofwithstanding high-speed sewing can be obtained.

Further, it is thought that ultrafine crystal nuclei are produced inpolyester filaments in which the orientation inhibitor is included toform a fibrous structure advantageous to heat-setting properties.

In the machine sewing thread of the invention, it is preferable to dyethe machine sewing thread by applying a tension so as not to causeshrinkage of the machine sewing thread in the dyeing step of the machinesewing thread in order to minimize the nonuniformity of stitches causedby loops. Specifically, a method for collapsing cheeses formed bywinding the machine sewing thread into the form of the cheeses in adyeing kettle and dyeing the many cheeses at a time can be adopted.According to the method, loops are not formed even in the case ofhigh-elongation filaments having high self-extensibility and a uniformfilament machine sewing thread can be obtained because a tension isapplied to the whole cheeses and the density of mutual filaments ishigh.

When the appearance of the machine sewing thread is to be spunized,loops can be developed by dyeing the machine sewing thread in a relaxedstate. In this case, however, it is preferable to thoroughly restrictthe formation of the loops to a small degree of spunizing of theappearance.

The present invention will be detailed by way of examples hereinafter.Physical properties in the examples were measured by the followingmethods.

(1) Intrinsic Viscosity [η]_(F)

The intrinsic viscosity was measured in o-chlorophenol at 25° C. by aconventional method. In the Examples 5 to 7, the intrinsic viscosity wasmeasured the filaments without the orientation inhibiter produced underthe same condition of the Examples.

(2) Lock Stitching High-speed Straight Sewability

Four T/R serges were sewn at a speed of 4000 rpm with a needle #14 byusing a lock stitching single needle sewing machine for one minute andevaluation was made by rating the case wherein the appearance wasrejected because the breakage of a machine sewing thread was present orsingle filament breakage frequently occurred as 1, the case whereinthere was no practical problem though single filament breakage extremelyslightly occurred as 2 and the case wherein no single filament breakageoccurred at all as 3.

(3) Back Stitching Sewability

One T/R serge was sewn at a speed of 2000 rpm with a needle #11 in theback direction by using a lock stitching single needle sewing machinefor 30 cm and evaluation was made by rating the case wherein theappearance was rejected because the breakage of a machine sewing threadwas present or single filament breakage frequently occurred as 1, thecase wherein there was no practical problem though single filamentbreakage extremely slightly occurred as 2 and the case wherein no singlefilament breakage occurred at all as 3.

EXAMPLES 1 TO 4 AND COMPARATIVE EXAMPLES 1 TO 3

(Production of Raw Yarns)

PET containing 0.02% by weight of titanium oxide was prepared as apolymer for polyester filaments A and PET without containing adelustering agent such as the titanium oxide was prepared as a polymerfor polyester filaments B. Both the polymers were respectively dried at160° C. for 4 hours.

Both the polymers were then melted at 300° C. The polymer for thepolyester filaments A was then discharged from 15 holes and the polymerfor the polyester filaments B was discharged from 5 holes by using abisected type spinneret, cooled and solidified with air at roomtemperature in a cross-flow quench stack provided under the spinneret. Afinish oil was applied to both the filaments in a combined filamentstate and the resulting yarn was then taken off at 1200 m/min to providean 180 dtex/20 filaments undrawn yarn. The undrawn yarn was composed of144 dtex polyester filaments A and 36 dtex polyester filaments B.

The undrawn yarn was fed to a drawing machine and drawn under thefollowing conditions. Namely, the undrawn yarn was wound around apreheating roller having a diameter of 90 mm and set at a surfacetemperature of 90° C. at a speed of 200 m/min by six turns and thenwound around a drawing setting roller having a diameter of 120 mm andset at a surface temperature of 140° C. at a speed of 600 m/min by fourturns to complete drawing and heat-setting. The resulting yarn wassubsequently wound around a secondary setting roller having a diameterof 120 mm and set at a surface temperature of 200° C. at a speed of 595m/min by four turns, subjected to heat-setting and then wound. Theaverage fineness of the resulting drawn yarn was 59 dtex.

(Production of Machine Sewing Threads)

S twists of 1050 T/M were applied to the drawn yarn. The resulting threeyarns were combined and Z twists at 700 T/M were applied to provide amachine sewing thread which was wound into cheeses. The obtained cheeseswere subjected to dyeing treatment at 130° C. for 40 minutes. Thecheeses were treated in a state of the drawn yarn under a tension by adyeing method for superimposing the cheeses and applying a compressionload.

After drying, 3% of a silicone finish oil was applied to afford machinesewing threads.

Table 1 shows performances of the resulting drawn yarns and machinesewing threads. The strength and elongation of the polyester filaments Aand the polyester filaments B in the drawn yarn are results obtained bymaking measurements of respective five single filaments randomly takenfrom the drawn yarns with a single filament strength and elongationmeasuring instrument as average values.

TABLE 1 Example Example Example Example 1 2 3 4 (1) (2) (3) Filaments AIntrinsic 1.11 1.11 0.98 0.72 0.62 0.85 1.11 Viscosity Strength 7.9 8.07.7 6.8 6.0 7.4 7.8 (g/dtex) Elongation 25 25 25 25 25 25 25 (%)Filaments B Intrinsic 0.42 0.64 0.64 0.51 0.42 0.75 0.31 ViscosityStrength 2.1 5.0 4.9 4.2 2.3 6.6 1.2 (g/dtex) Elongation 35 34 37 41 3930 48 (%) Difference in intrinsic 0.69 0.47 0.32 0.21 0.20 0.10 0.80Viscosity Drawn Yarn Strength 6.3 7.1 6.9 6.2 5.3 7.0 5.9 (g/dtex)Elongation 23 22 22 22 25 24 24 (%) Machine Sewing Thread Strength 5.76.1 5.9 5.3 4.6 5.9 5.7 (g/dtex) Elongation 26 24 24 64 29 27 24 (%)Lock Stitching High 2 3 3 3 1 3 1 speed Straight Sewability BackStitching 2 3 3 3 1 1 1 Sewability Notes: (1) means “Comparative Example1”. (2) means “Comparative Example 2”. (3) means “Comparative Example3”.

Example 1 showed good sewability in both lock stitching and backstitching. Some single filament breakage was found in the appearance ofthe machine sewing thread after sewing at a level without any problemfor practical use at all.

Examples 2 to 4 showed good sewability in both the lock stitching andthe back stitching without any problem at all and the appearance of themachine sewing thread was uniform and rich in gloss.

Breakage of the machine sewing thread occurred in both the lockstitching and the back stitching in Comparative Example 1.

Comparative Example 2 showed good sewability without any problem in thelock stitching at all; however, breakage of the machine sewing threadoccurred in the back stitching.

In Comparative Example 3, many single filament breakages and many singlefilament falloffs were caused in both the lock stitching and the backstitching and appearance was deficient in uniformity.

EXAMPLES 5 to 7 AND COMPARATIVE EXAMPLES 4 and 5

(Production of Raw Yarns)

PET without containing a delustering agent such as titanium oxide wasprepared as a polymer for polyester filaments A and PET withoutcontaining a delustering agent such as the titanium oxide was preparedas a polymer for the polyester filaments B. Both the polymers wererespectively dried at 160° C. for 4 hours.

The polymer for the polyester filaments B was then mixed with apolymethyl methacrylate (Delpet 80N manufactured by Asahi ChemicalIndustry Co., Ltd.) in a chip state in an amount of 0.5 to 8.0% as anorientation inhibitor and both the polymers were melted at 300° C. witha screw type melt extruder. The polymer for the polyester filaments Awas discharged from 15 holes and the polymer for the polyester filamentsB was discharged from 5 holes using a bisected type spinneret, cooledand solidified with air at room temperature in a cross-flow quench stackprovided under the spinneret. A finish oil was applied to both thefilaments in a combined state and the resulting yarn was taken up at1200 m/min to afford a 180 dtex/20 filaments undrawn yarn. The resultingundrawn yarn was composed of 144 dtex low-elongation filaments and 36dtex high-elongation filaments.

The resulting undrawn yarn was fed to a drawing machine and drawn underthe following conditions. Namely, the undrawn yarn was wound around apreheating roller having a diameter of 90 mm and set at a surfacetemperature of 90° C. at a speed of 200 m/min by 6 turn and then woundaround a drawing setting roller having a diameter of 120 mm and set at asurface temperature of 140° C. at a speed of 600 m/min by 4 turns tocomplete drawing and heat-setting. The resulting yarn was subsequentlywound around a secondary setting roller having a diameter of 120 mm andset at a surface temperature of 200° C. at a speed of 595 m/min by 4turns, heat-set and then wound. The average fineness of the drawn yarnwas 59 dtex.

(Production of Machine Sewing Threads)

S twists at 700 T/M were applied to the drawn yarn. The resulting threeyarns were combined and Z twists at 1050 T/M were then applied toprovide a machine sewing thread, which was wound into cheeses andsubjected to dyeing treatment at 130° C. for 40 minutes. The cheeseswere treated in a state of the drawn yarn under a tension by a dyeingmethod for superimposing the cheeses and applying a compression load.

After drying, 3% of a silicone finish oil was applied to afford machinesewing threads.

Table 2 shows performances of the resulting drawn yarns and machinesewing threads. Furthermore, the strength and elongation of thepolyester filaments A and the polyester filaments B in the drawn yarnare results obtained by making measurements of respective five singlefilaments randomly taken out from the drawn yarns with a single filamentstrength and elongation measuring instrument as average values.

TABLE 2 Example Example Example 5 6 7 Filaments A Intrinsic Viscosity0.88 0.88 0.88 Strength (g/dtex) 6.4 5.8 5.5 Elongation (%) 25 25 25Filaments B Intrinsic Viscosity 0.61 0.61 0.61 Amount of 0.5 5.0 8.0Orientation Inhibitor (%) Strength (g/dtex) 3.9 2.9 2.3 Elongation (%)55 74 89 Difference in intrinsic Viscosity 0.27 0.27 0.27 Drawn YarnStrength (g/dtex) 5.6 5.2 5.0 Elongation (%) 24 24 23 Machine SewingThread Strength (g/dtex) 4.9 4.6 4.3 Elongation (%) 27 27 26 LockStitching High-speed 3 3 2 Straight Sewability Back Stitching Sewability3 3 2

Examples 5 and 6 showed good sewability in both the lock stitching andthe back stitching without any problem at all and the appearance of themachine sewing thread was uniform and rich in gloss.

Example 7 showed good sewability in both the lock stitching and the backstitching. Some single filament breakage was found in appearance of themachine sewing thread after sewing at a level without any problem at allfor practical use.

INDUSTRIAL APPLICABILITY

According to the present invention, disadvantages caused by theformation of loops or slacknesses possessed by conventional machinesewing threads are improved, and there is provided a filament machinesewing thread capable of forming uniform stitches while leaving gloss offilaments and having good high-speed sewability.

What is claimed is:
 1. A filament machine sewing thread comprising aspun combined filament yarn obtained by combining polyester filaments Ahaving an intrinsic viscosity [η]_(F) within the range of 0.7 to 1.2with polyester filaments B having a lower intrinsic viscosity [η]_(F)than that of the polyester filaments A by 0.2 to 0.7 and a higherelongation than that of the polyester filaments A in a spinning stage.2. The filament machine sewing thread as claimed in claim 1, wherein afilament strength of the polyester filaments A is at least 5.0 g/dtex orabove.
 3. The filament machine sewing thread as claimed in any of claim1 or 2, wherein a filament strength of the polyester filaments B is atleast 1.3 g/dtex or above.
 4. The filament machine sewing thread asclaimed in claim 1, wherein a strength of the filament machine sewingthread is at least 4.0 g/dtex or above.
 5. The filament machine sewingthread as claimed in claim 1, wherein a mixing ratio of the polyesterfilaments A to the polyester filaments B is in the range of 7:3 to 9:1of the spun combined filament yarn.
 6. The filament machine sewingthread as claimed in claim 1, wherein the polyester filaments B containan orientation inhibitor.
 7. The filament machine sewing thread asclaimed in claim 6, wherein a content of the orientation inhibitor isthe range of 0.5 to 0.8 by weight based on a total weight of thepolyester filaments B.
 8. The filament machine sewing thread as claimedin claim 6, wherein the orientation inhibitor is at least one selectedfrom polystyrene polymers, polymethacrylate polymers andpolymethylpentene polymers.
 9. The filament machine sewing thread asclaimed in claim 2, wherein a strength of the filament machine sewingthread is at least 4.0 g/dtex or above.
 10. The filament machine sewingthread as claimed in 3, wherein a strength of the filament machinesewing thread is at least 4.0 g/dtex or above.
 11. The filament machinesewing thread as claimed in claim 2, wherein a mixing ratio of thepolyester filaments A to the polyester filaments B is in the range of7:3 to 9:1 of the spun combined filament yarn.
 12. The filament machinesewing thread as claimed in claim 3, wherein a mixing ratio of thepolyester filaments A to the polyester filaments B is in the range of7:3 to 9:1 of the spun combined filament yarn.
 13. The filament machinesewing thread as claimed in claim 4, wherein a mixing ratio of thepolyester filaments A to the polyester filaments B is in range of 7:3 to9:1 of the spun combined filament yarn.
 14. The filament machine sewingthread as claimed in claim 2, wherein the polyester filaments B containan orientation inhibitor.
 15. The filament machine sewing thread asclaimed in claim 3, wherein the polyester filaments B contain anorientation inhibitor.
 16. The filament machine sewing thread as claimedin claim 4, wherein the polyester filaments B contain an orientationinhibitor.